Hybrid lighter-than-air vehicle

ABSTRACT

The present invention is a variable geometry aircraft that is capable of morphing its shape from a symmetric cross-section buoyant craft to an asymmetric lifting body and even to a symmetric zero lift configuration. The aircraft may include variable span, length, and camber. The variability of the structure and the flexible envelope allows the aircraft to adjust its aspect ratio along with the camber of the upper and/or lower surfaces to achieve varying shapes. This transformation changes both the lift and drag characteristics of the craft and may be accomplished while the craft is airborne.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional application is a continuation in part of and claimspriority to PCT application No. PCT/US15/41490, entitled “HYBRIDLIGHTER-THAN-AIR VEHICLE,” filed Jul. 22, 2015 by the same inventor,which is a continuation of and claims priority to nonprovisionalapplication Ser. No. 14/746,332, entitled “HYBRID LIGHTER-THAN-AIRVEHICLE,” filed Jun. 22, 2015 by the same inventor, which is acontinuation in part of and claims priority to nonprovisionalapplication Ser. No. 14/515,079, entitled “HYBRID LIGHTER-THAN-AIRVEHICLE,” filed Oct. 15, 2014 by the same inventor, which is acontinuation in part of and claims priority to nonprovisionalapplication Ser. No. 14/341,184, entitled “HYBRID LIGHTER-THAN-AIRVEHICLE,” filed Jul. 25, 2014 by the same inventor.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates, generally, to aircrafts. More specifically, itrelates to aircrafts convertible between lighter-than-air andheavier-than-air configurations.

2. Brief Description of the Prior Art

Lighter-Than-Air (LTA) aircrafts have some characteristics not sharedwith Heavier-Than-Air (HTA) aircrafts in that they can maintain altitudewithout moving in a medium and can do so as long as buoyancy ismaintained. LTA aircrafts use low-density gas, such as helium orhydrogen to float in higher density air. These aircrafts usually employone or more gasbags filled with low-density gas to create a buoyancyforce that offsets the weight of the aircraft. The downside of LTAaircrafts is their large size, which is accompanied by large dragcharacteristics, preventing them from traveling at higher speeds. Thecurrent speed record for an LTA aircraft is 112 Km/hr (69.6 mph) but 56Km/hr is a common cruise speed.

HTA aircrafts use Newton's third law and Bernoulli's principle toachieve flight. These aircrafts are generally fixed wing or rotor wingaircraft. In either case, part or parts of the structure (e.g., wing,rotors, propellers, fuselage, and control surfaces) have acharacteristic shape called an airfoil. Airfoils are generallyasymmetric in cross-section with the upper surface having a greaterlength than the lower surface. This causes air moving across the uppersurface to travel faster than the air traveling across the lower surfacecausing a pressure decrease on the upper surface resulting in lift.

Lift can also be achieved/altered by altering the angle of attack (AoA)of an airfoil relative to the oncoming airflow. Increased AoA causesmass deflection resulting in lift (Newton's third law). Generally,increasing AoA increases lift until the angle reaches a point at whichthe airflow separates from the surface of the airfoil causingaerodynamic stall.

Regardless of means for creating lift, an HTA requires a wing-likestructure moving through a fluid. Movement requires a power source andno power source can last indefinitely. Therefore, the HTA aircrafts canonly maintain flight for limited periods of time. Even powerless glidershave duration limits as they trade airspeed for altitude gained fromthermal lift. The limitation in flight time of an HTA aircraft, however,is compensated by low drag characteristics and thus, high-speed flight.

The clear tradeoff between LTA and HTA aircrafts is speed verseindefinite flight. An ideal aircraft would have the ability of an LTA tohover, or station-keep, for extended periods for observation orsurveillance roles and also the ability of an HTA to operate athigh-speeds. This can theoretically be achieved through an aircraftconvertible between an LTA and an HTA configuration. Currently, thereexist hybrid convertible aircrafts, but none that provide a uniquecombination of attributes of both a fixed wing aircraft and a LTA craftallowing for indefinite mission durations, low energy station keeping,and the ability to dash at relatively high velocities.

U.S. Pat. No. 5,005,783 to James D. Taylor teaches a variable geometryairship capable of converting between a LTA and HTA airship. However,the airship is operationally complex and does not extend the operatingrange sufficiently to be practical as shown in Table 1. Along withmultiple other pitfalls, the shape and design of this airship preventsthe airship from transforming into both a symmetric neutral liftconfiguration and a negative lift configuration, thereby reducing theeffectiveness of the airship.

U.S. Pat. No. 4,102,519 to Edward L. Crosby, Jr. teaches a variable liftinflatable airfoil. However, this invention lacks internal moveablestructures, which prevent the airfoil from achieving multipleconfigurations. Additionally, the airfoil lacks a propulsion systemand/or control surfaces.

Accordingly, what is needed is an improved variable geometry aircrafthaving a simple, moveable internal structure to easily convert theaircraft between an LTA configuration and an HTA configuration. However,in view of the art considered as a whole at the time the presentinvention was made, it was not obvious to those of ordinary skill in thefield of this invention how the shortcomings of the prior art could beovercome.

All referenced publications are incorporated herein by reference intheir entirety. Furthermore, where a definition or use of a term in areference, which is incorporated by reference herein, is inconsistent orcontrary to the definition of that term provided herein, the definitionof that term provided herein applies and the definition of that term inthe reference does not apply.

While certain aspects of conventional technologies have been discussedto facilitate disclosure of the invention, Applicant in no way disclaimsthese technical aspects, and it is contemplated that the claimedinvention may encompass one or more of the conventional technicalaspects discussed herein.

The present invention may address one or more of the problems anddeficiencies of the prior art discussed above. However, it iscontemplated that the invention may prove useful in addressing otherproblems and deficiencies in a number of technical areas. Therefore, theclaimed invention should not necessarily be construed as limited toaddressing any of the particular problems or deficiencies discussedherein.

In this specification, where a document, act or item of knowledge isreferred to or discussed, this reference or discussion is not anadmission that the document, act or item of knowledge or any combinationthereof was at the priority date, publicly available, known to thepublic, part of common general knowledge, or otherwise constitutes priorart under the applicable statutory provisions; or is known to berelevant to an attempt to solve any problem with which thisspecification is concerned.

BRIEF SUMMARY OF THE INVENTION

The long-standing but heretofore unfulfilled need for an improvedvariable geometry aircraft having a simple, moveable internal structureto easily convert the aircraft between a lighter-than-air configurationand a heavier-than-air configuration is now met by a new, useful, andnonobvious invention.

The present invention includes a convertible design having alighter-than-air configuration and a heavier-than-air configuration witha flexible envelope in communication with a base structure. The presentinvention further includes adjustable longerons and length adjustingslack managers for varying the shape of the aircraft. Thelighter-than-air configuration typically has a span that is less thanthe span of the aircraft when in the heavier-than-air configuration.Further the aircraft may include a gas delivery for filing the envelopewith lighter-than-air gas when the aircraft is in the lighter-than-airconfiguration allowing for multiple translation cycles.

The base structure includes a central core, a port side outrigger, and astarboard side outrigger. In an embodiment, the core has an adjustablechord length directionally generally parallel with the longitudinal axisof the aircraft, such that the core is capable of adjusting at leastsome portion of the chord length of the flexible envelope. In anembodiment, the port side outrigger and the starboard side outriggereach have an adjustable chord length, such that at least some portion ofthe chord length of the flexible envelope adjusts as each outrigger'schord length adjusts. The lighter-than-air configuration is achieved inany geometry in which the volume of buoyant gas is sufficient to offsetthe weight of the aircraft and payload.

In addition to the central core, the base structure includes a leadingand trailing edge strut with both extending in a direction generallyperpendicular to and in communication with the central core. Theoutriggers extend in a direction typically parallel to the central coreand is in communication with the struts. Additionally, the basestructure is in communication with the moveable longerons and the slackmanagers. The central core may house a propulsion system to provide apowered aircraft or may house the mechanisms and/or lighter-than-air gascontainer(s), which would be more ideal for a glider embodiment.

The moveable longerons include upper and lower longerons. The upperlongerons are in communication with the flexible envelope and an uppertranslation assembly. In an embodiment, the upper translation assemblyhas an extended configuration where the moveable longerons are in a highcamber orientation and a retracted configuration where the uppermoveable longerons are in a low camber orientation. In transitioning tothe retracted configuration, the upper translation assembly moves theupper moveable longerons inward towards the lateral plane of theaircraft to decrease aircraft thickness. In transitioning to theextended configuration, the upper translation assembly moves themoveable longerons outward away from the lateral plane of the aircraftto place the upper moveable longerons in a more vertical orientation,which increases the aircraft thickness, compared to the orientation ofthe longerons in the retracted configuration.

Similarly, the lower longerons are in communication with the flexibleenvelope and a lower translation assembly. The lower translationassembly has an extended configuration where the moveable longerons arein a high camber orientation and a retracted configuration where thelower moveable longerons are in a low camber orientation. Intransitioning to the retracted configuration, the lower translationassembly moves the lower moveable longerons inward towards a lateralplane of the aircraft to decrease aircraft thickness. In transitioningto the extended configuration, the lower translation assembly moves themoveable longerons outward away from the lateral plane of the aircraftto place the lower moveable longerons in a more vertical orientation,which increases the aircraft's thickness, compared to the orientation ofthe longerons in the retracted configuration. An embodiment may includean upper translation assembly without a lower translation assembly or alower translation assembly without an upper translation assembly.

Multiple longeron translation mechanisms are envisioned for thisaircraft depending on aircraft size and mission. In an embodiment, eachtranslation assembly includes a translation motor fixed to the basestructure of the aircraft and a translation strap in communication withthe translation motor. The translation strap is a continuous loop fixedat one of the longerons and passes near an outrigger on the same side ofthe aircraft. When operated the motor causes the translation strap torotate, which in turn pulls the longeron towards or away from a centrallongitudinal axis of the aircraft.

The upper and lower moveable longerons each include a port side longeronand a starboard side longeron, wherein each longeron has a generallyairfoil or arc shape and a predetermined length that extends ingenerally the same direction as the central longitudinal axis of theaircraft. Moreover, the moveable longerons are in a generally verticalorientation when in the high camber position and in an acute angleorientation when in the low camber position.

The length-adjusting slack managers comprise of a port side slackmanager and a starboard side slack manager. Each arm has a generally arcshape, is subjected to a bias force attempting to force each arm in adirection away from the central longitudinal axis of the aircraftresulting in an increased arc shape, and is in communication with theflexible envelope. Additionally, each slack manager has a retractedposition and an expanded position, where in the retracted position, thelength and arc of the slack manager is at a minimum and in the expandedposition, the length and arc of the slack manager is at a maximum. Theretracted position is achieved when a tension force in the flexibleenvelope overcomes the bias force, resulting from the transition of themoveable longerons towards a more vertical orientation, thereby reducingthe length and arc of the slack manager. Contrastingly, the expandedposition is achieved when the tension force in the flexible envelope isovercome by the bias force, resulting from the transition of themoveable longerons to a more horizontal orientation, thereby increasingthe length and arc of the slack manager. Due to the positioning of theslack managers, the span of the aircraft is directly affected by thetransition between the retracted position and the extended position.

In an embodiment, the slack manager is an anisotropic beam having two ormore composite rods with cross members extending between the rods. Thecross members are designed to have a predetermined spring constantembedded into the structure. One of the composite rods is pivotallyattached to the aircraft and one or more of the composite rods areanchored against the pivot structure to provide a source of the tension.

-   -   The present invention further includes a structural connection        point to connect the base structure with the moveable longerons        and the slack managers. The structural connection point has a        first fixed connection attached to an outrigger, a second fixed        connection attached to a strut, a first pivoting connection        attached to one of the upper moveable longeron, a second        pivoting connection attached to one of the lower moveable        longeron, and a third pivoting connection attached to one of the        slack managers.

In an embodiment, the aircraft uses a gas storage and retrieval systemadapted to house, distribute, and retrieve lighter-than-air gas. Thissystem allows the aircraft to easily convert between a lighter-than-airconfiguration and a heavier-than-air configuration multiple timeswithout having to refill on gas.

Multiple internal payload carrying methods are envisioned for theaircraft. In an embodiment, the aircraft includes a propulsion systemthat includes an electrical generator system adapted to convert windenergy into electrical energy while the aircraft is in thelighter-than-air configuration. In an embodiment, flexible solar panelsare attached to an exterior surface of the envelope to retrieve andconvert solar energy into electrical energy to extend mission time.

In an embodiment, the aircraft has a payload hard point attached to thelower translation assembly to facilitate the attachment and managementof external payloads in addition to payloads attached internally to thecore structure. In an embodiment, the aircraft includes additionalstructural features, referred to as a wing load management system, toimprove the wing loading capabilities that might be necessary whentransporting heavy payloads. The wing load management system may includestrap spars and support ribs for load distribution. A certain embodimentincludes a payload hard point attached to the core of the aircraft andthe envelope attached to the sides of the payload hard point such thatsome portion of the payload hard point is external to the envelope.

An embodiment may include at least some portion of the flexible envelopehaving an accordion-like structure. In an embodiment, the leading and/ortrailing edge strut may be out of plane with the chord line.

These and other important objects, advantages, and features of theinvention will become clear as this disclosure proceeds.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts that will beexemplified in the disclosure set forth hereinafter and the scope of theinvention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference should be made tothe following detailed description, taken in connection with theaccompanying drawings, in which:

FIG. 1 is a perspective view of an embodiment of the present inventionin an LTA configuration.

FIG. 2 is a perspective view of an embodiment of the present inventionin a negative lift configuration.

FIG. 3 is a side view of an embodiment of the present invention shown ina positive lift configuration.

FIG. 4A is a side view of the present invention in an LTA configuration.

FIG. 4B is a front view of the present invention in an LTAconfiguration.

FIG. 5A is a side view of the present invention in the dashconfiguration.

FIG. 5B is a perspective view of the present invention in the dashconfiguration.

FIG. 5C is a front view of the present invention in the dashconfiguration.

FIG. 6 is a perspective view of an embodiment of the present inventionshowing the internal structural components of the aircraft.

FIG. 7 is an exploded view of an embodiment of a structural connectionpoint.

FIG. 8 is a rear perspective view of the starboard side of an embodimentof the present invention showing the internal structural components ofthe aircraft.

FIG. 9A is a top view of the internal base structure of an embodiment ofthe present invention.

FIG. 9B is a top view of the internal base structure of an embodiment ofthe present invention shown in a folded configuration.

FIG. 10 is a rear perspective view of the starboard side of anembodiment of the present invention showing the internal structuralcomponents of the strap spar and spreading rib version of the aircraft.

FIG. 11 is a front view of an embodiment of the present invention havinga dihedral wing shape.

FIG. 12 is a perspective view of an embodiment of a mechanically drivenversion of the upper translation assembly.

FIG. 13A is front view of an embodiment of the gear driven uppertranslation assembly in an extended configuration.

FIG. 13B is front view of an embodiment of the gear driven uppertranslation assembly in a retracted configuration.

FIG. 14 is a front view of an embodiment of the lower translationassembly, having a payload hard point, while in an extended orientation.

FIG. 15 is a top view of FIG. 14.

FIG. 16 is a front view of the lower translation assembly shown in FIG.14 while in a retracted orientation.

FIG. 17 is a bottom view of FIG. 16.

FIG. 18 is a partial front view of an embodiment of the aircraftemploying the flexible translation assembly illustrating the movement ofa bottom longeron, from a vertical orientation, towards the core of theaircraft as the translation strap rotates in a clockwise direction. Thefigure also illustrates a telescoping leading and trailing edgeembodiment.

FIG. 19 is a partial front view of the port side of an embodiment of theaircraft highlighting the flexible translation assemblies and theflexible envelope attached to the external payload hard point.

FIG. 20A is a side view of an embodiment of a mechanically drivennon-pivoting longeron.

FIG. 20B is a sectional view of the embodiment in FIG. 20A.

FIG. 21 is a side view of an embodiment of a non-pivoting longeron.

FIG. 22 is an embodiment of the slack manager.

FIG. 23 is a perspective view of an embodiment of the present inventionillustrating the preferable location of reinforcement layers.

FIG. 24 is a perspective view of an embodiment showing possibleconfiguration of internal panels used to create compartmentalized gasbladders.

FIG. 25 is a front view of an embodiment highlighting the bottom portside of the flexible envelope.

FIG. 26 is a sectional view of the highlighted portion in FIG. 34,illustrating the accordion-like surface.

FIG. 27 illustrates how the accordion-like surface of the section of theenvelope expands as the aircraft transforms between the LTAconfiguration and a HTA configuration.

FIG. 28 illustrates how the accordion-like surface of the section of theenvelope expands as the aircraft transforms between the LTAconfiguration and the dash configuration.

FIG. 29 is a perspective view of an embodiment of the aircraft.

FIG. 30 is a side view of an embodiment of the present invention shownin a positive lift configuration.

FIG. 31 is a side view of an embodiment of the present invention in anLTA configuration.

FIG. 32 is a side view of an embodiment of the present invention in thedash configuration.

FIG. 33 is a perspective view of an embodiment of a detachable tailsection.

FIG. 34 is a rear view of the embodiment in FIG. 33.

FIG. 35 is a side view of the embodiment in FIG. 33.

FIG. 36A is a rear view of the embodiment shown in FIG. 33, highlightingthe rotation of the control surfaces.

FIG. 36B is a rear view of the embodiment shown in FIG. 33, highlightingthe rotation of the control surfaces.

FIG. 37 is a captured output for a symmetric airfoil with high thicknessas a percentage of chord that was achieved using FoilSim software.

FIG. 38 is a captured output for a symmetric airfoil with low thicknessas a percentage of chord that was achieved using FoilSim software.

FIG. 39 is a captured output for an asymmetric airfoil with lowthickness as a percentage of chord that was achieved using FoilSimsoftware.

FIG. 40A is a perspective view of an embodiment of the present inventionhaving a variable chord length.

FIG. 40B is a side view of FIG. 40A.

FIG. 41 is a perspective view of an embodiment of the present inventionhaving a variable chord length at the outriggers.

FIG. 42 is a perspective view of an embodiment of the present inventionhaving a variable chord length.

FIG. 43 is front view of an embodiment in the LTA configuration. Thetranslation assemblies are removed from the figure for clarity.

FIG. 44 is a front view of the embodiment in FIG. 39 with thetelescoping leading and trailing edge struts telescoped inward toshorten the length of each strut in preparation for storage. Theenvelope and translation assemblies are removed from the figure forclarity.

FIG. 45 is a front view of the embodiment from FIGS. 39 and 40 with theenvelope extension arms collapsed, the distal ends of the starboard sidelongerons brought together, and the distal ends of the port sidelongerons brought together to allow the longerons to be easily wrappedaround the core of the aircraft. The envelope and translation assembliesare removed from the figure for clarity.

FIG. 46 is a front view of the longerons wrapped around the core toallow for easy storage and transportation of the aircraft. The envelopeand translation assemblies are removed from the figure for clarity.

FIG. 47 is a perspective view of an embodiment of the aircrafthighlighting the telescoping leading and trailing edge struts attachedto an oval-shaped core having an external payload hard point. Thelongerons, envelope, and translation assembly are removed from thefigure for clarity.

FIG. 48 is a perspective view of an embodiment having a cargo palletattached to the aircraft.

FIG. 49 is a front view of an embodiment employing two upper translationassemblies and two lower translation assemblies to providequadrant-based camber manipulation.

FIG. 50 is a perspective view of an embodiment of the upper translationassembly having a single motor operating two pulleys to simultaneouslyalter the orientation of the upper port and starboard side longerons.

FIG. 51 is a table that provides both specific examples and generalcharacteristics of various configurations.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings, which form a partthereof, and within which are shown by way of illustration specificembodiments by which the invention may be practiced. It is to beunderstood that other embodiments may be utilized and structural changesmay be made without departing from the scope of the invention.

Glossary of Claim Terms

Envelope: is a lightweight flexible material.

Chord Line: is a straight line extending between the leading edge andtrailing edge of the envelope.

Heavier-Than-Air Configuration: is a configuration of the aircraft thatcannot maintain altitude without moving through a medium to createBernoulli lift or changing the angle of attack.

Lighter-Than-Air Configuration: is a configuration of the aircraft thathas a buoyancy to weight ratio greater than 1:1.

Longeron: is a structural member of the aircraft.

Outrigger: is a structural member designed to resist compression thatextends in generally the same direction as the longitudinal axis of theaircraft.

Payload Hard Point: is an attachment point for payloads or instrumentscarried on or within the aircraft.

Propulsion System: is a system capable of moving the aircraft through amedium.

Strut: is a rod or bar forming part of a framework and designed toresist compression.

As best illustrated in FIGS. 1-5, the present invention is a variablegeometry aircraft capable of morphing its shape from a buoyant crafthaving a generally symmetric cross-section (FIG. 4) to an asymmetriclifting body configuration (FIGS. 1-3) or to a low camber symmetricshape (FIG. 5). Additionally, the aircraft is capable of achieving anyshape between the buoyant symmetric cross-section and the low cambersymmetric shape. The camber-transformation can be accomplished while thecraft is airborne and does not require any ground support equipment.

The aircraft may include one or more gas containers coupled to a gasdelivery and preferably retrieval system. The gas delivery system fillsthe internal volume of the flexible envelope with lighter than air gas,while the retrieval system is adapted to recover any gas alreadycontained in the internal volume of the flexible envelope. These twosystems allow for easy transformation between the LTA and HTAconfigurations. In an embodiment, the aircraft may include a valvesystem for venting gas out of the aircraft and into the atmosphere.

When the aircraft is in the LTA configuration, the aircraft has all ofthe traditional characteristics of a blimp for station keeping, verticaltake-off/landing or slow speed flight. By adjusting the shape of thesurface to achieve an airfoil shape, the craft can augment the buoyancyby creating aerodynamic lift to increase its duration of flight or actas a conventional unpowered glider. Moreover, by reshaping both theupper and lower surfaces, the craft can achieve a relatively low dragconfiguration (hereinafter the “dash” configuration) for high velocityflight (in excess of 200 km/hr for smaller aircraft sizes) to rapidlyreposition itself or fly high velocity missions.

The aircraft is also highly portable, light weight, relatively silent inoperation, inexpensive to produce and operate, and has a uniquestructure that allows it to operate even if the gas envelope ispenetrated. Although there are numerous other aircraft technologies,this device can operate across a number of operating envelopes andperforms multiple roles very well without significant compromise (seeTable 1 below).

TABLE 1 Aircraft Comparison Velocity Range Operating OperationalAircraft (kts) Cost Complexity Duration Rotor/VTOL 0-115 (217*) HighHigh Low Fixed Wing 50+ Low-High Low-Med Low LTA 0-30 (60*) Low Low-MedHigh Hybrid LTA** 0-40  High High Med Present Invention 0-200 Low LowHigh *World Record **Only viable recorded device defined in U.S. Pat.No. 5,005,783

As illustrated above, the present invention fills a unique performanceniche in that, with low complexity and high reliability, a unique andbroad range of performance feats can be achieved. The unique designfeatures of the present design, taken in combination, make it animprovement on the technology for LTA aircraft, hybrid LTA aircraft, andfixed wing flying bodies, especially as applied to unmanned vehicles.

The aircraft's nearly infinite variability stems from, among otherthings, the interrelation of moveable longerons, slack managers, and aflexible envelope. The base structure, moveable longerons, and slackmanagers are all enclosed in a flexible yet durable envelope. Longerons102 and 104 extend outward a variable distance from a lateral plane ofthe aircraft to adjust the camber/thickness of the upper and/or lowersurfaces. Slack managers 120 extend outwardly in an arch shape from thebase structure on the port and starboard sides in a generally planardirection (lateral plane) with respect to the base structure andcomprised of at least two telescoping sections. Slack managers 120 aresubject to a biasing force, which forces slack managers 120 to extend inlength creating a larger arch shape. As a result, slack managers 120 areable to keep envelope 122 taught as longerons 102 and 104 adjust thethickness of the aircraft.

Aircraft Performance

Due to the variable geometry capabilities, the aircraft will have arange of performance characteristics spanning from a high Coefficient ofDrag (C_(D)) seen in the LTA configuration to a relatively low C_(D)seen in the flying wing configuration. The lift characteristics willalso vary from a lift neutral symmetric configuration to a positive liftor negative lift airfoil shape to suit mission requirements. Theseconfigurations can be changed dynamically while airborne to suit missionneeds. The driving requirement for the aircraft is the desired dashspeed of approximately 200 kts for small aircraft sizes. The assessmentof performance and structural characteristics has been completed forthree different configurations of craft defined by the length/chord ofthe aircraft and the span of the central, airfoil shaped portion of thecraft, defined by the outriggers and struts. The alternative drivingcharacteristic is to support large payloads, but this requirement doesnot drive motor size.

Dash Speed Calculation

The truly innovative and functionally distinct orientation found in noother LTA to HTA convertible aircraft, is the dash configuration. Asshown in FIGS. 5a and 5b , the dash configuration is an approximatelysymmetric HTA configuration achieved when both upper translationassembly 106 and lower translation assembly 107 are in the retractedposition. In this position, the upper and lower moveable longerons 106,107 are pulled inwardly towards core 114 where they reside in a morehorizontal orientation to substantially reduce the thickness and camberof the aircraft.

Among the novel characteristics of this aircraft is the speed at whichthe aircraft is capable of traveling when in the dash configuration andpowered by a propulsion system. The equation in Table 2 is used tocalculate the amount of force required to move a body through a viscousmedium. This is used to derive the thrust (and therefore number and sizeof motors) to achieve the required speed; thus driving other factorssuch as weight, power, envelope size, etc. The initial calculation is todetermine the minimum motor output required to achieve the desiredmaximum dash velocity of 230 mph at a cruise altitude of 10,000 feet MSLfor an aircraft of a specific size. FIG. 51 shows both specific examplesand general characteristics of various configurations. Using amathematical simulation tool, (FoilSim II) available from NASA, theC_(D) for various configurations of the aircraft from a large chord tolength ratio to a small chord to length ration was calculated. As seenin FIG. 51, the low chord to length ratio with a highly symmetricprofile yields a curve of thrust required to achieve a velocity and isreflected by curves for each of the example aircraft sizes. Note thataircraft size drives buoyant gas volume and; therefore, maximum payloadshown in the FIG. 51 examples. This small chord thickness yields thelowest C_(D) and therefore, the lowest motor size to achieve the desiredspeeds. A standard radio controlled motor thrust has been chosen and isindicated by the vertical lines in the thrust portion of FIG. 51 toreflect combinations of multiple motors of the same size. This providesthe number of motors required to achieve the desired dash velocity.Given the aircraft size (therefore payload), desired speed, and motorconfiguration, specific examples are given for predicted operationalranges for various power supply configurations assuming no batteryrecharging or additional buoyant gas source. The FoilSim model outputcorresponding to a specific performance case is shown in FIG. 38. It isapparent that the maximum LTA speed in the highly buoyant configuration(high thickness to chord length ratios) will be nowhere near thoseachieved in the dash configuration. FIGS. 37 and 38 show the output fortwo of the symmetric configurations examined using the FoilSimsimulation program. FIG. 39 shows how C_(D) increases in the asymmetricconfiguration while also experiencing a corresponding increase in thecoefficient of lift (C_(L)). The data shows that in this configuration,significant aerodynamic lift can be achieved by this design at 0 degreeAoA. Higher lift performance can be achieved at higher AoA.

TABLE 2 Desired speed in knots: 200 kts = 102.88 m/sec Fr = .5(C_(D)) *ρ_(air) * v² * A_(s) Assume Altitude of 10000 ft and Speed of 250 ktsAltitude 10000 ft = 3048 m Speed: 230 mph = 200 kts = 370 km/hr 102.88 vVelocity (m/sec): in this model, this is an input characteristic anddrives the motor size. - 0.4135 ρ_(air) Density of Air: is a function ofatmospheric conditions and varies A Surface Area (m²) C_(D) Coefficientof Drag: using FoilSim III

Base Structure

Referring now to FIG. 6, the base structure of an embodiment of theaircraft includes a generally rectangular frame comprising of leadingand trailing edge struts 116 connected to port and starboard outriggers118. Core(s) 114 also serve as a key structural base by helping supportthe leading and trailing edge struts 116. The two outriggers 118 arepreferably generally parallel to core 114 and leading and trailing edgestruts 116 are generally perpendicular to core 114 however, sweptconfigurations are also considered. Outriggers 118 provide structure aswell as an attachment point for mounting moveable longerons 102 and 104and slack managers 120. It should be noted that leading and trailingedge struts 116 may pass through core 114 as shown in FIGS. 1-10 or maybe disposed above or below core 114 as depicted in FIGS. 18, 19, and43-46.

Connection points 136 interconnect leading and trailing edge struts 116with outriggers 118. If the aircraft is viewed from the perspective oftwo halves—a port and starboard side, each half/side includes a pair ofstructural connection points 136. In addition, each side of the aircraftincludes a slack manager 120 and a pair of moveable longerons—moveableupper longeron 102 and moveable lower longeron 104. As illustrated bestin FIGS. 7-8, slack manager 120 and longerons 102 and 104 are alsoconnected to the structural connection points 136.

Referring now to FIG. 7, an embodiment of structural connection point136 includes five connections, excluding a connection for an additionalsupport member. The connections of moveable longerons 102 and 104 andthe connection for slack manager 120 are pivoting connections, such asball joints. Strut 116 and outrigger 118 connections are preferablyfixed connections. The pivoting connections for moveable longerons 102and 104 and slack manager 120 aid in the convertibility of the aircraft.The fixed connections of strut 116 and outrigger 118 aid in the rigidityof the base structure to improve the aircraft's ability to operate underthe typical forces and stresses associated with flight. In anembodiment, the connection for slack manager 120 is spring loaded toproduce tension on slack manager 120 in turn transferring the tensiononto the envelope; thereby removing slack in the dash configuration.

In an embodiment, as shown in FIG. 8, the base structure may include anadditional support member 138. Support member 138 is included toincrease the rigidity of the base structure and may be connected to thebase structure at any location known to a person having ordinary skillin the art, such that the structure improves rigidity. Multiple supportmembers may be included depending on aircraft configuration. It shouldbe noted that the base structure would include support structure 138 onboth the port and starboard sides of the aircraft, but FIG. 8 is limitedto the starboard section of the aircraft to reduce clutter.

Also illustrated in FIG. 8 is the open space between core 114 andoutrigger 118. This open space allows for the storage of the additionalsystems that will likely be used in operation. The additional systemsare preferably mounted to the core 114 and may include, but are notlimited to batteries, computation devices including the navigationsystem, control computer, battery charger and control device,navigation, servo motors, internal payload elements, buoyant gas andstructural components for the envelope.

Referring now to FIGS. 9A and 9B, an embodiment includes strut-to-coreconnection points 140 and support member-to-core connection points 137.Connection points 140 pivotally connect struts 116 to core 114, andconnection points 137 pivotally connect support members 138 to core 114.As a result, the base structure of the aircraft can fold to a morecompact orientation and improve transportability of the aircraft. FIG.9B also illustrates an embodiment having slideable outrigger-to-supportmember connection points 139, which slides along outrigger 118 to aid infolding the aircraft.

Referring now to FIG. 10, an embodiment of the base structure includes awing load management system. Note that FIG. 10 provides only thestarboard side in an attempt to improve the clarity of the figure. Thewing load management system is designed to accommodate payloads having aweight many times greater than that of the aircraft. Additionally, thesystem helps maintain the aircraft's center of gravity/weight andbalance as well as maintain the underside airfoil shape critical toaerodynamic performance. The system includes one or more strap spars 148extending in the span direction. Note that the Strap Spars do notcommunicate with the Longerons or impede their motion. Strap spars 148are preferably flexible and made from Kevlar, or a similar strong,flexible, and lightweight material. Strap spars 148 extend from core 114to slack manager 120 on either side of the aircraft to providewingtip-to-wingtip load distribution. The flexibility of strap spars 148allow the slack managers to contract inward towards the core whenconverting to the LTA configuration.

Strap spars 148 preferably pass underneath one or more support riblets160, having an arc or airfoil shape, to maintain the airfoil shape andfurther decrease wingtip curvature under heavy loading. The wing loadmanagement system may also include support ribs (not shown) runningbetween leading and trailing edge struts 116 on either side of core 114acting as load distributors aiding in maintaining the underside airfoilcontour. In an embodiment, the support ribs and strap spars 148 may beintertwined as is known by a person having ordinary skill in the art tofurther increase load distribution.

Polyhedral Wing Shape

In an embodiment, the leading edge strut and/or the trailing edge strutmay each be curved or may each comprise of a two or more structuralmembers creating independent port side and starboard side struts. As aresult, the HTA configuration has a wing shape, such as a polyhedralwing shape, that is angled with respect to the local horizontal. Asshown in FIG. 11, port side struts 316 a and starboard side struts 316 bare attached to core 314 at a positive angle with respect to the localhorizontal resulting in a dihedral. The angle may vary in magnitude anddirection depending on the required aerodynamic performance. The leadingedge and/or trailing edge struts may also be oriented so that they arenot perpendicular to the core yielding a swept leading and/or trailingedge.

Adjustable Longerons

The movement or adjustment of the longerons alters the camber/thicknessof the upper and/or lower surfaces to achieve differing body shapes. Thelongerons are non-linear, preferably having a curved shape. As a resultof the curvature, each longeron has a vertex—the local maximum or peakof the curvature of the longeron. The vertex is a point along thecurvature of the longeron that is furthest from the lateral axis of theaircraft at any given time or orientation. The longerons are adjustableto vary the distance the vertex extends from the lateral axis of theaircraft. In an embodiment, the longerons have a fixed length todecrease complexity of the aircraft, however, length-adjusting longeronsare also considered.

In an embodiment, the longerons may have a common pivot point, such thatthe longerons have a generally V-shape orientation with respect to eachother when viewed from above. The common pivot point could be locatedtowards the front and/or rear of the aircraft. Additionally, the lowerlongerons may also have a common pivot point located towards the frontor rear of the aircraft. The V-shaped orientation doubles the number ofskin support points with a possible reduction in flutter. This may bereplicated at multiple points along the span to increase skin shapemanagement.

Rigid Translation Assembly

In an embodiment, as best shown in FIGS. 1-5, moveable longerons 102 and104 are adapted to pivot between a generally vertical orientation and agenerally horizontal orientation. By pivoting, the distance between thelateral axis and the vertices can be adjusted, which in turn adjusts theaircraft's thickness. The orientation of moveable longerons 102 and 104is controlled by a camber-adjustment assembly (also referred to as atranslation assembly). The translation assemblies can be mounted bothabove and below the core of the aircraft allowing both the top andbottom halves to change in shape and thickness. Moveable upper longerons102 and moveable lower longerons 104 are each in communication withupper translation assembly 106 and lower translation assembly 107,respectively.

Referring to FIGS. 12-17, the translation assemblies each include motor108, gear assembly 110, and extendable arms 112. In an embodiment, thecenter of gear assembly 110 is attached to the envelope to aid inmaintaining proper envelope positioning. As shown in FIG. 17A,extendable arms 112 are attached to upper moveable longerons 102. Whenupper translation assembly 106 is in the extended configuration, uppermoveable longerons 102 are in a generally vertical orientation.Contrastingly, FIG. 17B shows upper translation assembly 106 in theretracted configuration, with the moveable longerons 102 pulled inwardlytowards motor 108.

Referring now to FIGS. 14-17, an embodiment includes payload hard points147 on translation assemblies 106 and 107. Most commonly, the hard pointwould be located on the lower translation assembly 107. FIGS. 14 and 15show lower translation assembly 107 in the extended configuration andFIGS. 16 and 17 show the translation assembly in the retractedconfiguration. Payload hard points 147 provide an attachment structurefor securing payloads to the exterior of the aircraft envelope. In anembodiment, payload hard point 147 on lower translation assembly 107 isexternally located with respect to the envelope. In this embodiment,extendable arms 112 are in communication with lower moveable longeronsinside of the envelope while payload hard point 147 extends downwardsand out of the envelope allowing certain payloads to be attached outsideof the envelope.

Strap Translation Assembly

Referring now to FIGS. 18-19, an embodiment may use a strap-basedtranslation assembly. FIG. 18 provides a bottom port side sectional viewof the embodiment employing the flexible translation assemblies. Theembodiment preferably includes an upper translation assembly (not shownto reduce clutter) and a lower translation assembly each having motor308 in communication with port and starboard side translation straps312. Motor 308 is located near, and preferably attached to, core 314.Note that there is an analogous arrangement on the starboard side.

Referring now to FIG. 49, independent upper and lower translationassemblies allow the aircraft to alter the camber of the top and bottomof the aircraft independently. An embodiment may include independentport and starboard side translation straps. As a result, the embodimenthas the ability to independently vary the shape of each of theaircraft's four quadrants—a top starboard quadrant, a top port quadrant,a bottom starboard quadrant, and a bottom port quadrant. This embodimentallows for roll and pitch control of the aircraft as shown in FIG. 49.

In an embodiment shown in FIG. 50, the upper translation assembly andlower translation assembly each include a motor having two pulleys incommunication with one another, such that the rotation of one pulleyresults in the opposite rotation of the other pulley. One pulley is incommunication with the starboard translation strap, while the otherpulley is in communication with the port side translation strap. Thus,the motor on the upper translation assembly controls the uppertranslation assembly and the motor on the lower translation assemblycontrols the lower translation assembly, creating two independenthalves, as shown in FIG. 49.

As shown in FIGS. 18 and 19, each translation strap 312 is a continuousloop fixed at one of the longerons (either the upper longeron 302 orlower longeron 304 depending on the location of translation strap 312).The continuous loop is in communication with motor 308 and passes aroundoutrigger 318. Motor 308 is adapted to rotate continuous translationstrap 312 in either a clockwise or a counterclockwise direction, tocause the translation strap to pull the attached longeron either towardsor away from core 314.

FIG. 18 provides a sectional view of the bottom port side of theaircraft to highlight the movement of longeron 304 with the rotation oftranslation strap 312. As motor 308 rotates translation strap 312 in aclockwise direction, longeron 304 is pulled towards core 314 to decreasethe camber and alter flight characteristics. In a similar manner, thedirection of rotation can be reversed to pull longeron 304 away fromcore 314. To maintain constant tension, an embodiment may include aspring loaded recoil system to maintain constant tension in thetranslation straps.

It is contemplated that the motor may be located anywhere on theaircraft and the translation strap may pass through a pulley locatednear the outrigger rather than passing around the outrigger itself.Furthermore, translation strap may be linear rather than a continuousloop with one end attached to the longeron and the other incommunication with the motor. Such an embodiment would require anadditional mechanism to force the longeron away from the core when thetension in the translation strap is decreased. It should be noted thatthe continuous translation strap fixed at the longeron also providesstructural support as a spar strap.

The strap translation assembly may employ any number of motors andtranslation straps to improve the ease of re-orienting the longerons. Anembodiment may include two straps for each side of the translationassembly. For example, the upper portside translation assembly may havetwo translation straps secured to the upper portside longeron. A firsttranslation strap may be fixed on the upper longeron closer to the aftend of the longeron and a second strap would be fixed on the upperlongeron closer to the fore end of the longeron. As an added benefit,each translation strap may communicate with an independently operatedmotor, thereby allowing the aircraft to warp the wing between the foreand aft ends of the aircraft.

Non-Pivoting Longerons

An embodiment may include longerons secured to the base structurethrough a non-pivoting connection point. Rather than alter the camber bypivoting between a generally vertical orientation and a generallyhorizontal orientation, the longerons alter the camber and aircraftthickness by altering the distance in which the longerons projectoutwardly from the base structure of the aircraft. In an embodiment, thelongerons include at least two sections telescoping with respect to eachother, such that the length can be adjusted. The adjustable lengthallows for the alteration of the distance that the vertices of thelongerons extend outwardly from the base structure. The longerons havean effective maximum length, which occurs when the envelope is fullyinflated, and an effective minimum length, which occurs when theaircraft is in the dash mode.

As shown in FIG. 20, an embodiment of non-pivoting longerons 500includes first flexible section 554 in telescoping communication withsemi-rigid or rigid section 556. Rigid section 556 is located towardsthe aft end of the aircraft where the longeron experiences minimal shapealteration to account for the rigidity of the section. Gear assembly 558is secured at some point along the fore half of rigid section 556 and isin communication with flexible section 554. As the gear in gear assembly558 rotates, the location of flexible section 554 translates withrespect to rigid section 556 such that the total length of longerons 500is adjustable. Longeron 500 is at a minimum length when flexible section554 is fully retracted within rigid section 556 and is at a maximumlength when flexible section 554 is fully extended from rigid section556. While a gear assembly is described, it is considered that anymechanical drive capable of altering the relative location of twotelescoping members may be used.

As shown in FIG. 20B, the cross-section of flexible section 554 may havea T-shape. The T-shape provides an increase in the structural stabilityand aids in preventing rotation of flexible section 554 with respect torigid section 556. A T-shape is illustrated but other forms may beincorporated to manage loads.

As shown in FIG. 21, an embodiment of non-pivoting longeron 600 includespiston 660 driving flexible section 654. Piston 660 can be any type ofpiston, such as a pneumatic or hydraulic piston. Piston 660 is in fluidcommunication with a fluid tank (not shown) through conduit 656, and anelectronic valve controls the fluidic pressure during operation. Piston654 is located towards the aft end of the aircraft where the longeronexperiences minimal shape alteration to account for the rigidity of thepiston.

An embodiment of the non-pivoting longeron may include an extensionmember having one end secured to a longeron and the other end secured tothe base structure of the aircraft. The extension member can increase inlength such that the longeron is extended outwards away from the lateralaxis of the aircraft when the extension member increases in length.Similarly, the longeron will be pulled inwardly towards the lateral axisof the aircraft when the extension member decreases in length. Inaddition, the extension member may be angled from the center or backhalf of the base structure towards the front half of longeron. Thespecific attachment location and angle of the extension member can becalculated to provide an optimum resistance to the aerodynamic forcesapplied on the longerons during flight.

Slack Managers

As the longerons transition from a thick camber, as shown in FIG. 4B,towards a thin camber position, as shown in FIG. 5C, slack managers 120extend outward to keep envelop 122 taught. As a result, slack managers120 ultimately increase the span of the aircraft as seen in comparingFIG. 5C to FIG. 4B. In reversing the orientation of moveable longerons102 and 104 from a thinner camber position to a thicker camber position,envelope 122 overcomes the biasing force imposed on slack managers 120causing slack manager 120 to shorten in length, which ultimatelydecreases the span of the aircraft and maintains envelope tension.

Slack managers 120 may be employed to remove slack in the flexibleenvelope to enable high speed flight with minimum envelope flutter. Onthe smaller sized aircraft, slack managers 120 comprise of telescopingtubes and tension is provided through spring loaded features on thestructural connection points 136. On larger versions, however, thetelescoping tube design is likely less effective than the use of aunique anisotropic beam as shown in FIG. 22.

The anisotropic beam includes two or more composite rods (preferably athree-rod configuration) with spring steel cross members embedded intothe structure. The spring constant (controlled by material and length)varies across the length of the beam to provide variable tension on theenvelope to compensate for the pressure on the envelope. One or more ofthe composite rods interfaces with the pivot joint assembly at both endsto provide the source of the tension while the other rod(s) are anchoredagainst the pivot structure. Any twisting or translation of the rodsrelative to each other is prevented by the spring steel cross members.The design allows different spring constants to be used along the lengthof the structure by adjusting the stiffness and lengths of the crossmembers. As a result, the pressure on the envelope at the tips andtrailing edge can be significantly reduced while pressure at the leadingedge can be maintained. This feature provides superior tension controlwith a lightweight structure and significantly reduces envelope flutterin the dash mode.

As illustrated in FIG. 22, the cross section of slack manager 120 ispreferably triangular in shape with two rods 144 fixed to cross membertrusses (made up of cross members 142) and a third rod 146 slidablyattached to the cross member trusses. This unique assembly providesslack manager 120 with a variable length while also allowing for varyingstructural support depending on the strength of the individual crossmember trusses located along the length of slack manager 120. Thisdesign may also incorporate a telescoping connecting rod to the aftjoint for continuity of wing tip shape.

Envelope

The variability of the aircraft imposes several requirements on flexibleenvelope 122. For example, flexible envelope 122 must be flexible toaccommodate the shape morphing capability, have a very low permeabilityto Helium, and be lightweight. As a result, the envelope is preferablymade from a plastic sheet material. This material is prone to twonegative features that will affect the performance of the LTA in thedash configuration and impact performance overall. One is flutter of theenvelope, which increases drag and causes aerodynamic instability. Thesecond is the possibility of penetration of the envelope by airbornehazards (such as insects, birds, or debris) at the high speeds.

The possibility of penetration may be avoided by the installation ofleading edge shields 127 that are hinged on the leading edge strut andcan expand or contract with the movement of the envelope. See FIG. 1.Additionally, mechanical stops can be installed to reflect the shape ofthe leading edge in the dash configuration to remove the possibility offlutter at high speeds. Flutter may also be reduced by management ofinternal gas pressure and/or the addition of multiple longerons or otherinternal structural elements.

Referring now to FIG. 23, an embodiment of envelope 122 includesinternal reinforcement layer 130 and a secondary containment bag tofacilitate Helium recovery. The moveable structural components of theaircraft raise concerns regarding structural members rubbing on a fairlythin plastic surface and ultimately causing the envelope to fail.Therefore, reinforcement layers 130 are located in areas likely toexperience increased wear and tear from the moveable internal structureof the aircraft. Reinforcement layers 130 are made of Mylar or someother wear resistant, lightweight, and flexible material, to increasethe serviceable life of the envelope. In an embodiment, thereinforcement layer is also added to areas likely to experience debrisimpact, such as the leading edge and under the translation assemblies.

FIG. 24 shows internal gas partition panels that create separate gasbladders within the envelope. The partition panels act as flexible wallscreating four independent chambers. The partition panels include toppanel 131, bottom panel 132, starboard panel 133, and port panel 134.Top panel 131 runs between the outriggers and rests on the central core,both of which are not shown to aid in clearly identifying the internalpanels. Bottom panel 132 also runs between the outriggers, but islocated under the central core. Both the port and starboard panels 134and 133 run between the top and bottom longerons on the respective sidesof the aircraft. The panels are preferably made from the same materialas the envelope, however any lightweight flexible and airtight materialknown to a person having ordinary skill in the art may be used. Thesepanels aid in the recovery of the low-density gas used in the LTAconfiguration. The partition bladders also reduce the possibility ofcatastrophic gas loss if the envelope integrity is violated. Additionaldividers or bladders may be included depending on aircraft mission andconfiguration.

Alternate embodiments of the aircraft may include an envelope havingvarying elasticity. For example, smaller aircrafts may have a generallyelastic envelope, mid-sized aircraft may have sections in the lobe/wingtip area that have material of different elasticity integrated inpatches into the skin, and large aircraft may have an accordion-like orsemi rigid surface as shown in FIGS. 25-38. FIGS. 26-28 show thetransition of the port side lower lobe transitioning from the LTAconfiguration to an HTA configuration and illustrate the alteration ofthe accordion-like portion of envelope 322 from a compressed position toan extended position. Along with easing the ability of the craft totransform between the HTA and LTA configurations, the accordion-likeenvelope may also act as a flow disturbance to maintain laminar flowover the surface of the aircraft.

The envelope may also include sections on the underside that are morerigid than the rest of the envelope to provide a landing surface for theaircraft. In an embodiment, these sections are strategically arranged asis known to a person having ordinary skill in the art to provide alanding surface for water landings. The landing surface for waterlandings is designed such that the amount of surface area in contactwith the water is small enough to enable the lifting force created bythe aircraft, when in the LTA configuration, to overcome the surfacetension of the water.

In an embodiment, the envelope may have an opening, preferablyreseal-able, that facilitates maintenance, deconstruction, andtransportation. In an embodiment, the envelope may include anindependent closure mechanism, as is known to a person having ordinaryskill in the art, for temporarily sealing the flexible envelope aroundthe internal structures of the aircraft.

Propulsion System

In an embodiment, the present invention includes a central, tubular corecontaining a propulsion system. The propulsion system is preferably anElectronic Ducted Fan (EDF) motor. An embodiment may include severalcores depending on the size of the aircraft and the missionrequirements. In addition, these cores can be located anywhere about thebody of the aircraft and may include any type of propulsion system knownto a person of ordinary skill in the art, such that the location andtype of propulsion system does not interfere with the convertibility ofthe aircraft.

Referring back to Table 2, the motor size and number of motors arederived for each of the three configurations to determine ifcommercially available EDF motors can be used in the design. The dataproves that a single 3000 gmf motor is sufficient to achieve the desiredvelocity for the 1-meter-by-1-meter sized aircraft. This size motor isreadily available for Radio Control (RC) aircraft. For larger sizecraft, the number of core units would be increased to provide therequired thrust. This assessment shows that two core units of roughlythe same size as above will propel a 2-meter-by-2-meter design. Largermotors or core combinations of four motors would be required for the4-meter-by-4-meter design. In an embodiment, any number and type ofmotors may be used as is known to a person having ordinary skill in theart.

Glider Embodiment

An embodiment of the aircraft may lack a propulsion system, such thatthe HTA configuration results in a glider. The glider embodiment of thepresent invention reflects a logical adaptation of this powered designto a non-powered glider design. The glider embodiment would be uniquelycapable of independently reaching sufficient altitude (through the LTAconfiguration), such that traditional shore-based Reception, Staging,Onward Movement, and Integration (RSOI) logistics depots could beoverflown and bypassed. Additionally, the glider is capable of ferryinga variety of supply classes directly to the point of need using the wingload management system with an order of magnitude cost reduction overcurrent methods. Moreover, the design organically incorporates anall-weather launch capability that enables scalable parallel sorties forhigh system throughput.

In an embodiment, the non-powered glider includes core(s) for structuralsupport and/or for gas container(s). The core further providesattachment points for additional equipment and may serve as a leadcomponent in adjusting the aircraft's chord length in a variable chordembodiment discussed further down.

As provided in Table 4 below, the glider embodiment provides anexcellent solution in all areas and is clearly superior in the areas ofcost/complexity to deploy, mission adaptability, and all-weatherperformance.

TABLE 4 CONTROLLED FIXED WING PARACHUTE/SOFT TRADITIONAL PRESENTPARAMETER GLIDER AUTO GYRO GLIDER LTA INVENTION RECURRING UNIT COSTModerate High Low Low Low SUPPORT/DEPLOYMENT High High Low Low Low COSTCOMPLEXITY Moderate High Low Low Low GROUND SUPPORT High Impact - LaunchHigh Impact - Launch High to Mod - Air Low - generally Low - Selfdeploying EQUIPMENT REQUIRED system need to get system need to get dropfrom cargo tethers and securing system requires only aircraft to initialaircraft to initial aircraft posts are sufficient attachment to thealtitude. Methods altitude. Methods for most LTA cargo pallet, leveling(tow/JATO/ground (tow/air launch) aircraft and release. launch) requirerequire extensive extensive ground or ground or shipboard. shipboard.PAYLOAD CAPACITY Moderate - aircraft Moderate - aircraft Moderate -aircraft Moderate - aircraft Moderate - aircraft AS A FUNCTION OF THEwould need to be very would need to be very would need to be would needto be would need to be very 463L PALLET large to carry full large tocarry full very large to carry very large to carry large to carry full463L pallet 463L pallet full 463L pallet full 463L pallet 463L palletCONTROLLABILITY TO Moderate - good to Moderate - good to Moderate - goodLow - without High - highly TARGET LOCATION target but one landingtarget but one landing to target but one power, very difficultadjustable flight path, only only landing only to adjust for evenw/environmental environment condition changes TRANSPORT AND Low - evenwith Low - even with High - package Moderate - may High - shipped in aHANDLING folding wings or other folding wings or other similar totraditional require considerable small, stackable CONVENIENCEcomponents, aircraft components, aircraft parachute storage volumecontainer tube and will require large will require large fully ready toexpand storage space storage space and inflate LAUNCH COMPLEXITY High -Launch to High - Launch to Moderate - process Moderate - may Low - Selfdeploying altitude requires altitude requires of loading and requireconsiderable system requires only significant significant deploymentfrom storage volume attachment to the infrastructure infrastructure dropaircraft well cargo pallet, leveling regardless of launch regardless oflaunch defined but takes and release. method. method. cargo aircraftinto harm's way. RETRIEVAL High - Requires High to Mod - High to Mod -High to Mod - Low - Conversion to COMPLEXITY extensive clearanceRequires moderately Requires moderately Requires moderately full orpartial LTA area for descent and large clearance for large clearance forlarge clearance for allows for vertical landing. approach and landingapproach and landing approach and landing descent. LOADING High HighModerate Low Low COMPLEXITY/TIME TO LOAD COMPLEXITY/TIME TO High HighLow Moderate Low UNLOAD THROUGHPUT COST High High Moderate High Low

Hybrid Rotor Embodiment

An embodiment, as shown in FIGS. 29-32, includes a plurality of rotors450 to combine the functionality of a rotor craft with theshape-shifting abilities of the present invention. The embodimentincludes an extended core 414 that projects beyond envelope 422 in boththe fore and aft directions to provide a structure on which rotors 450can be externally mounted. Each rotor 450 is secured to rotor structuralmember 452, which is in turn secured to core 414. In an embodiment,rotor structural member 452 passes through core 414 to secure a rotor450 on both the starboard and port sides of the aircraft. An embodimentmay also include rotors 450 pivotally secured to rotor structural member452 to increase the thrust vectoring capabilities of the aircraft.

The rotor structures provide additional flight controlling features toimprove the control and maneuverability of the aircraft. For example,the rotor structures enable the aircraft to perform vertical takeoff andlandings at a greater speed and control than would be possible withoutthe rotors. These rotors may pivot on multiple axes to provide oraugment control (pitch, yaw and/or roll), and thrust (vertical orhorizontal).

Stability and Control Components

Referring back to FIGS. 1-5, the aircraft also includes flight stabilityand control components, such as elevons 124 (which may be substituted byan elevator/aileron configuration and/or thrust vectoring), verticalstabilizer 125, rudder 126, leading edge shield 127, and propulsionsystem 128. The pair of rear-mounted elevons 124 perform the function ofboth elevators and ailerons to control pitch and roll. Both arecontrolled via servos and a microprocessor mounted to the core assembly.Yaw control/directional stability is provided through rudder 126 mountedto vertical stabilizer 125. Another multiple control surfaceconfiguration is depicted in FIG. 33 that reduces aircraft weight andcomplexity.

An embodiment may include rudder 126 configured to project into theducted fan airstream to provide a degree of thrust vectoring for verylow speed flight and low velocity maneuvering. It is envisioned that thelarger sizes of this LTA would employ thrust vectoring entirely as itsmethod of directional control for certain applications as depicted inFIG. 33. Thrust vectoring with multiple motors and larger sizes wouldsignificantly reduce the weight of the aircraft and provide superiormaneuvering capability over conventional control surfaces.

An embodiment may include supplementary thrust vectoring to aid inflight control of the aircraft, particularly during low speed LTAoperations. The aircraft may include supplemental thrust vectoringlocated generally at each corner of the base structure. The thrust couldoriginate from a manifold running from the central core to vectoringnozzles or could originate from a separate motor(s) dedicated to thesupplementary thrust vectoring. Another source of thrust could originatefrom venting internal pressure using a set of valved nozzles. The sourceof the vented pressure is preferably another gas container that isseparate from the lighter-than-air gas tank. The additional gascontainer may store and release atmospheric gas.

In an embodiment, the aircraft may include a center of mass (CM)management system. The CM management system can modify the angle ofattack and roll by shifting mass in the aircraft, similar to a pilotshifting weight to control a hang-glider.

Detachable Tail

An embodiment of the aircraft may include a detachable tail section. Thedetachable tail section mates to the base structure of the aircraftwithout impacting the airtight seal and may include control surfaces.

Referring now to FIGS. 33-36, detachable tail 700 includes controlsurfaces 724 (that may be configured as elevons, ruddervators, aelerons,elevators and/or rudders, depending on flight mode) pivotally connectedto tail core 762 through rotational element 764. Motors 766 control therotation of the control surfaces 724 about the longitudinal axis of thecontrol surfaces as depicted by directional arrows 770 shown in FIG.36A. In an embodiment, non-rotating (stabilizing fins) or additionalrotating control surfaces might be added for various mission profiles.In addition to the control surfaces 724, detachable tail 700 alsoemploys thrust vectoring cone 768 to further control the flight of theaircraft.

In an embodiment, as shown in FIG. 36B, control surfaces 724 may berotationally secured to tail core 762. As a result, control surfaces 724may be rotationally reoriented as depicted by arrows 766. Exemplaryarrows 766 illustrate a counter-clockwise rotation, but control surfaces724 are adapted to rotate both in a clockwise and counter-clockwisedirection. This rotation allows each control surface 724 to act inmultiple roles without additional structural members. For example, thecontrol surfaces can achieve 3 entirely distinct orientations: 1) thecontrol surfaces can be oriented in a vertically aligned position (oneupward and one downward) to act as moving or non-moving verticalstabilizers when the aircraft is configured in a low speed LTAconfiguration; 2) the control surfaces can be oriented approximately asshown in FIG. 34 to operate as aileron/elevator/elevons for moderatespeed flight in a high lift camber position; and 3) the control surfacescan be oriented approximately horizontally to provide minimumcoefficient of drag flight control during high speed flight. Inaddition, non-rotating (stabilizing fins) or additional rotating controlsurfaces might be added for various mission profiles.

In an embodiment a detachable tail 700 is intended to removably fastento core 114 by sliding core 762 into core 114. As a result, the outerdiameter of tail core 762 is slightly smaller than the inner diameter ofcore 114. This arrangement allows envelope 122 to seal around core 114while tail 700 slides into core 114 without interfering with the sealbetween envelope 122 and core 114. This same concept applies to theattachment of forward and/or aft rotors as described in the Hybrid RotorEmbodiment.

FIGS. 33-36 depict the control surfaces extending downward in agenerally V-shape orientation. In an embodiment, the control surface maybe oriented to extend upward and/or the tail may include one or moreadditional control surfaces extending outwardly from the tail core andmay be either fixed (as stabilizing fins) or articulating (as control ortrim surfaces).

Variable Chord Length Embodiment

In an embodiment, as shown in FIGS. 40-42, at least some portion of theaircraft has a variable chord length—the distance between the trailingand leading edges. An adjustable chord length provides the aircraft withanother method of altering the aspect ratio and in turn the performanceof the aircraft. Additionally, the adjustment of the chord lengthprovides the aircraft with another method of or an additional aid intransforming between the LTA and HTA configurations.

As shown in FIG. 40, the dash configuration can be achieved bylengthening the chord of the aircraft. The length of the chord can bereduced to create the symmetric LTA configuration shown in FIG. 4.Additionally, this embodiment may include the upper and lowertranslation assemblies to further manipulate the lifting characteristicsand to allow for nearly an infinite array of aircraft shapes.

The variable chord feature may be achieved in any manner known to aperson having ordinary skill in the art. In an embodiment, the entiretrailing edge strut is adapted to move when adjusting the aircraft'schord length. The adjustment may be accomplished through a drivemechanism such as collet 250, which mechanically lengthens core 214 onwhich the trailing edge strut is secured. Outriggers 218, longerons 202and 204, and slack managers 220 may also include similar collets (notshown) to allow these members to adjust in length. In an embodiment, thelongerons 202 and 204, outriggers 218, and slack managers 220 arestructurally designed to telescope and are each subjected to an inherentbiasing force trying to extend their respective chord lengths. When thecore's chord length extends, taking trailing edge strut 216 with it,longerons 202 and 204, outriggers 218, and slack managers 220 eachextend in length due to their respective inherent biases. Shortening thechord length would be achieved by shortening the core's chord using adrive mechanism with enough force to overcome the biasing forces onlongerons 202 and 204, outriggers 218, and slack managers 220.

The length adjusting capabilities of the core, longerons, outriggers,and slack managers may be accomplished by any method(s) or mechanism(s)known to a person having ordinary skill in the art. Additionally, thecore and/or the length adjusting mechanism of the core may be incommunication with the longerons, outriggers, and slack managers to helpadjust their lengths or each may be controlled to move independentlyfrom the others.

In another embodiment, the trailing edge of the flexible envelope may beadapted to allow the outriggers and/or longerons to extend outside ofthe envelope. The core may be directly responsible for adjusting thelocation of the trailing edge strut, while the outriggers have anon-adjustable chord length. This embodiment would result in someportion of both the outriggers and the longerons extending out from thetrailing edge of the flexible envelope in the aft direction when thechord length of the flexible envelope is shortened. This embodimentprovides a less complex version to reduce the number of moving parts andthe potential problems inherently associated with moving parts.

Referring now to FIGS. 41-42, an embodiment may include a trailing edgestrut comprised of two structural members allowing the port andstarboard elevons to be angularly oriented with respect to one another.Such an embodiment allows for further manipulation of the aircraft'sstability and flight performance. As shown in FIG. 41, core 214 may benon-adjustable or simply remain retracted in chord length whileoutriggers 218, longerons 202 and 204, and slack managers 220 increasein chord length. As a result, each elevon 224 forms an acute angle withits nearest outrigger 218. Contrastingly, FIG. 38 provides an example ofcore 214 in an extend chord length position, with outriggers 218 andlongerons 202 and 204 in a non-adjustable or a retracted chord lengthposition. As a result, each elevon 224 forms an obtuse angle with itsnearest outrigger 218. Each of the configurations above offers a uniquestability and performance profile.

Variable Span Embodiment

In an embodiment, as shown in FIG. 43, leading edge strut 316 and thetrailing edge strut (not visible) each have an adjustable length suchthat the span of the aircraft can be altered. The struts preferablyinclude a telescoping design, but may include any length adjustingdesign known to a person having ordinary skill in the art. Moreover, thelength may be manually or automatically adjustable. The struts mayinclude intervals at which the struts are capable of locking atpredetermined lengths. Such an embodiment may also include rigid supportspars having similar length adjusting abilities or may employ flexiblestrap spars as is shown in FIG. 10. In an embodiment, each strut may beadjusted independently, such that the span of one strut may be variedwith respect to the span of the other strut to further increase thevariability of the aircraft's aerodynamic characteristics.

Flexible Collapsible Embodiment

Referring now to FIGS. 44-46, an embodiment is designed to enable theaircraft to reduce in size and fit into a tubular container. Theembodiment includes several features enabling the reduction in size,including adjustable length struts, semi-rigid longerons, and flexibletranslation assemblies. Adjustable length leading edge strut 316 andtrailing edge strut (not shown) enable the span of the aircraft toshorten. Semi-rigid longerons 302, 304 flex to encircle core 314 andstruts 316 (when reduced in length). The longerons are resilient enoughto return to operational positions when released. Each flexibletranslation assembly includes translation strap(s) 312 and motor 308(shown in FIGS. 18 and 19).

The flexible translation assemblies enable the aircraft to be rolled upfor easier transportation. As shown in FIGS. 44-46, the leading andtrailing edge struts 316 telescope down into a reduced length, whichsignificantly reduces the span of the aircraft. Then, slack managers 320are forced towards the central longitudinal axis of the aircraft asshown in FIG. 45. Finally, longerons 302 and 304 are rotated around core314 as shown in FIGS. 45-46. The aircraft is then stored in a tubularcontainer or restrained with cargo straps to greatly improve the easewith which the aircraft can be transported.

As highlighted in FIG. 47, the embodiment employing a strap basedtranslation assembly includes payload hard point 347 attached to core314. FIG. 47 does not include the longerons or the envelope to improveclarity. There may be any number of payload hard points 347 extending inany direction. As shown in FIG. 19, envelope 322 may attach to the edgeof payload hard point 347 to provide an externally located payload hardpoint 347.

As shown in FIG. 48, the aircraft may include cargo straps 352 adaptedto attach to external cargo pallet 354. Cargo straps 352 are incommunication with the structure of the aircraft and pass through theenvelope. Cargo pallet 354 is preferably made of lightweight materialsin a structurally sound configuration. For example, cargo pallet 354 mayinclude a balsa or honeycomb core covered with a carbon fiber sheet.Additionally, cargo pallet 354 preferably has an aerodynamic profile.

Cargo straps 352 may be adjustable in length or include a mechanism forreeling the straps towards core 314. Thus, the entire assembly can tuckinto the underside of the aircraft and has an aerodynamic profilesimilar to that of the flying wing configuration. Such an embodimentwill likely include an envelope having sections with varying elasticity.For example, the portion of the envelope spanning the length of theextended leading and trailing edge struts 316 may be generally inelasticsuch that the location of the passage of cargo straps 352 through theenvelope remains consistent throughout the conversions between LTA andHTA configurations. The other portions of the envelope may have greateror lesser elasticity to enable easier transitions between configurationsas is known to a person having ordinary skill in the art. Furthermore,the envelope may have a differing elastic modulus along different axes.For example, the envelope may have greater elasticity along the spanthan along the chord length.

Outrigger Versatility

In an embodiment, the outriggers may be thrust tubes to providedifferential thrust as flight a control method. In another embodiment,the outriggers may be gas tubes for storing additional lighter-than-airgas. The outrigger tubes may also carry liquid gas to supplement thelighter-than-air gasses inside the envelope and facilitate multiplere-inflation cycles with or without recovering gas from the envelope orused for other purposes.

Energy Generation/Recovery

An embodiment of the aircraft may be equipped with flexible solar panelsmounted to the upper exterior surface of the envelope to extended onstation performance. This allows the aircraft to remain in the LTAconfiguration and hover while the system batteries are recharged. Energyrecovery through the EDF, when equipped, is also available while inbuoyant mode if turned into an oncoming airstream.

Fuel cells may be used to generate electricity for battery systemcharging directly powering aircraft electrical systems or otherpurposes. Additionally, waste Hydrogen from the fuel cell process may beused to augment the buoyant gas within the envelope.

Communication

An embodiment may include communication or antenna components. Theantenna array provides additional operational capabilities, such assurveillance, communication, or radar interference. In an embodiment,the structure and envelope may be shaped or made of a material lesslikely to impede the transmission of electromagnetic waves. Antennaelements may also be embedded in the envelope surface.

The advantages set forth above, and those made apparent from theforegoing description, are efficiently attained. Since certain changesmay be made in the above construction without departing from the scopeof the invention, it is intended that all matters contained in theforegoing description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

Cargo and Payload Attachment

Various cargo and payload management techniques have been discussed invarious embodiments aforementioned. The highly versatile design allowsfor the stowage of cargo, attachment of payloads and sensors, andmounting of sensors in internal and/or external locations. FIGS. 18, 19,and 48 depict an external hardpoint that reduces gas volume, but allowsfor easy payload attachment. Additionally, the design accommodatesexternally accessible core tubes if external access is required andother external hard points as depicted in FIGS. 14-17. Furthermore, theinnovative design allows for mounting of payloads, not requiringfrequent external access, to be mounted directly to the core or otherinternal structure and/or the aircraft skin. Such an embodiment,however, has provisions for one or more re-sealable penetrations thatallow access for payload management and/or maintenance.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention that, as amatter of language, might be said to fall therebetween.

What is claimed is:
 1. An aircraft comprising: a convertible designhaving a lighter-than-air configuration and a heavier-than-airconfiguration; a flexible envelope in communication with a basestructure, wherein the flexible envelope has a leading edge and atrailing edge creating a chord line; a span extending from a port sidewingtip to a starboard side wingtip; the lighter-than-air configurationincluding the aircraft having a span that is less than the span of theaircraft when in the heavier-than-air configuration; a hollow core tubeextending between an aft end and a fore end of the aircraft, wherein thehollow core tube is in open fluid communication with an ambientenvironment; and a pair of control surfaces extending outwardly in aradial direction from an aft end of the hollow core tube, wherein eachcontrol surface is adapted to rotate about a longitudinal axis of thehollow core tube and pivot about a radial axis with respect to thehollow core tube.
 2. The aircraft of claim 1, wherein the base structureincludes the hollow core tube, a port side outrigger, and a starboardside outrigger, the hollow core tube has an adjustable chord lengthdirectionally parallel with a longitudinal axis of the aircraft, suchthat the hollow core tube is capable of adjusting at least some portionof the chord length of the aircraft.
 3. The aircraft of claim 2, whereinthe port side outrigger and the starboard side outrigger each have anadjustable chord length, such that at least some portion of the chordlength of the aircraft adjusts as each outrigger's chord length adjusts.4. The aircraft of claim 1, wherein the base structure further includesa leading edge strut extending in a direction perpendicular to and incommunication with the hollow core tube, a trailing edge strut extendingin a direction perpendicular to and in communication with the hollowcore tube, a port side outrigger extending in a direction parallel tothe hollow core tube and in communication with the leading and trailingedge struts, and a starboard side outrigger extending in a directionparallel to the hollow core tube and in communication with the leadingand trailing edge struts.
 5. The aircraft of claim 1, furthercomprising: upper adjustable longerons and lower adjustable longerons,wherein the upper adjustable longerons are in communication with thebase structure, the flexible envelope, and an upper translationassembly, and the lower adjustable longerons are in communication withthe base structure, the flexible envelope, and a lower translationassembly; each translation assembly having an extended configurationwhere their respective adjustable longerons are in a high camberorientation and a retracted configuration where their respectiveadjustable longerons are in a low camber orientation, in transitioningto the retracted configuration, each translation assembly moves theirrespective adjustable longerons inward towards a central longitudinalaxis of the aircraft to decrease aircraft thickness, and intransitioning to the extended configuration, the adjustable longeronsmove outward away from the central longitudinal axis of the aircraft toincrease the aircraft thickness; a length-adjusting slack manager incommunication with the flexible envelope and subject to a bias forceattempting to force the slack manager outward in a direction away fromthe central longitudinal axis of the aircraft; and the length-adjustingslack manager having a retracted position and an expanded position,wherein the length-adjusting slack manager is capable of transitioningbetween the retracted and expanded positions to alter the shape of theflexible envelope.
 6. The aircraft of claim 5, wherein the upper andlower adjustable longerons each include a port side longeron and astarboard side longeron, wherein each longeron has a chord lengthextending between the leading edge and the trailing edge of theaircraft.
 7. The aircraft of claim 5, wherein the slack manager is ananisotropic beam including two or more composite rods with cross membershaving a predetermined spring constant embedded into the structure, oneof the composite rods is pivotally attached to the aircraft and one ormore of the composite rods is anchored against the pivot structure toprovide a source of the tension.
 8. The aircraft of claim 5, furtherincluding a port side slack manager and a starboard side slack manager,wherein each slack manager has an arc shape and an adjustable chordlength in the same direction as the central longitudinal axis of theaircraft.
 9. The aircraft of claim 5, wherein the adjustable longeronsare extended in length to achieve camber modification.
 10. The aircraftof claim 5, wherein the adjustable longerons are in a verticalorientation, with respect to the span of the aircraft, when in the highcamber orientation and the adjustable longerons are in an acute angleorientation, with respect to the span of the aircraft, when in the lowcamber orientation.
 11. The aircraft of claim 10, further comprising awing load management system including a plurality of rigid supportingribs extending between the leading edge strut and the trailing edgestrut and a plurality of flexible strap spars extending between thehollow core tube and the slack manager.
 12. The aircraft of claim 11,wherein the plurality of rigid supporting ribs have an adjustable chordlength.
 13. The aircraft of claim 10, wherein the leading edge strut andtrailing edge strut have adjustable lengths.
 14. The aircraft of claim1, further comprising a gas storage and retrieval system adapted tohouse, distribute, and retrieve lighter-than-air gas.
 15. The aircraftof claim 1, further comprising a propulsion system residing within thehollow core tube.
 16. The aircraft of claim 1, further comprising: upperadjustable longerons and lower adjustable longerons, wherein the upperadjustable longerons are in communication with the base structure, theflexible envelope, and an upper translation assembly, and the loweradjustable longerons are in communication with the base structure, theflexible envelope, and a lower translation assembly; and eachtranslation assembly includes a translation motor fixed to the basestructure of the aircraft and a translation strap in communication withthe translation motor, the translation strap is a continuous loop fixedat one of the longerons and passes near an outrigger on the same side ofthe aircraft, when operated the motor causes the translation strap torotate, which in turn pulls the longeron towards or away from a centrallongitudinal axis of the aircraft.
 17. The aircraft of claim 1, whereinthe flexible envelope includes at least some portion having anaccordion-like structure.
 18. The aircraft of claim 1, further includinga payload hard point external to the envelope.
 19. An aircraftcomprising: a convertible design having a lighter-than-air configurationand a heavier-than-air configuration; a flexible envelope incommunication with a base structure, wherein the flexible envelope has aleading edge and a trailing edge creating a chord line; a span extendingfrom a port side wingtip to a starboard side wingtip; thelighter-than-air configuration including the aircraft having a span thatis less than the span of the aircraft when in the heavier-than-airconfiguration; a hollow core tube in mechanical communication with theflexible envelope, the hollow core tube extending between an aft end anda fore end of the aircraft, wherein the hollow core tube is in openfluid communication with an ambient environment; and a control surfacesecured to an aft end of the hollow core tube and extending outwardly ina radial direction from the aft end of the hollow core tube, at least aportion of the control surface adapted to rotate about a longitudinalaxis of the hollow core tube and pivot about a radial axis with respectto the hollow core tube.
 20. An aircraft comprising: a convertibledesign having a lighter-than-air configuration and a heavier-than-airconfiguration; a flexible envelope in communication with a basestructure, wherein the flexible envelope has a leading edge and atrailing edge creating a chord line; a span extending from a port sidewingtip to a starboard side wingtip; the span of the aircraft beingequal to or greater than the chord line of the aircraft when in both theheavier-than-air configuration and the lighter-than-air configuration; ahollow core tube in mechanical communication with the flexible envelope,the hollow core tube extending between an aft end and a fore end of theaircraft, wherein the hollow core tube is in open fluid communicationwith an ambient fluid; and a control surface secured to an aft end ofthe hollow core tube and extending outwardly in a radial direction fromthe aft end of the hollow core tube, at least a portion of the controlsurface adapted to rotate about a longitudinal axis of the hollow coretube and pivot about a radial axis with respect to the hollow core tube.